The monitoring stations set up to enforce the Comprehensive Nuclear Test Ban Treaty could also help scientists to better understand earthquakes and the makeup of the Earth's interior.

The United States undertook the Apollo program to demonstrate its technological superiority over the world; learning about the moon and setting off "a revolution in planetary science" was just a side effect, David Strangway of Quest University said at this weekend's American Association for the Advancement of Science meeting in Boston. The U.S. built magnetometers in World War II so the Navy could scout the sea for places to hide. It just so happened that scientists used that magnetic mapping data to figure out how fast the seafloor was spreading.

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The next geopolitical/military tech to offer a huge side bonus to science? If Strangway is right, it's going to be the network of sensors set up to monitor activity for the Comprehensive Nuclear Test Ban Treaty.

As was reported earlier this week, those sensors picked up evidence of the claimed North Korean nuclear test. Raymond Jeanloz of the University of California, Berkeley, who also spoke at the talk, said the nearly 300 detectors now operational could pinpoint the location of the North Korean test to within hundreds of meters. He showed meeting attendees satellite photos of the test sites, saying that where once this monitoring was the domain of only military intelligence services, now the public at large can access these kinds of images.

But while the International Monitoring System fulfills its political purpose, it will also provide unprecedented data to Earth scientists. In one example, Miaki Ishii of Harvard said that researchers can use the worldwide network to see seismic waves that have traveled through the planet from earthquakes on the other side of the world. They way those waves change as they move through the Earth's hot inner core, as compared to waves that didn't pass through that region, can tell you something about the core itself. We know today that the inner core is smaller in diameter than the moon, but 34 percent more massive, Ishii said. Seismic readings are revealing more about the very center of that, the innermost inner core, which spans just 300 km (186 mi) in diameter.

What's next for seismic monitoring? "It will open doors we can even dream of," Strangway said.